Catalytic Aryl-Aryl Coupling via Cleavage of C-H or C-C Bond

We have developed a number of direct, regioselective arylation reactions of appropriately functionalized aromatic compounds via C-H bond cleavage. Thus, treatment of the substrates including phenols, aromatic ketones and amides, and benzylic alcohols with aryl halides under palladium catalysis gives the corresponding ortho-arylated products. In combination with α-arylation, which is also catalyzed by palladium multiple arylation of the substrates can proceed by a single treatment with excess aryl halides to produce oligoaryl compounds. On the other hand, we have also found that tert-benzyl alcohols undergo arylation via not only C-H but also C-C bond cleavage accompanied by liberation of ketones to afford biaryls. In this account are summarized these new coupling reactions.